1. Field of the Invention
This invention relates to a glazed insulating unit with improved edge insulation, the unit having three or more spaced sheets, and more particularly, to a triple-glazed insulating unit having adjacent sheets separated by a spacer frame wherein the spacer frames are offset from one another.
2. Presently Practiced Technology
At the present time the majority of insulating glazing units includes a pair of glass sheets separated by a spacer frame. In general and not limiting to the discussion, the units having metal spacer frames, e.g. of the type shown in FIGS. 1, 3, 4 and 10 of U.S. Pat. No. 5,655,282 are fabricated by applying a moisture impervious adhesive or sealant on outer opposed surfaces of a metal spacer frame and positioning the spacer frame between a pair of sheets to form a subassembly. The subassembly is conveyed though a heated oven to heat the adhesive after which the subassembly passes between pressing rolls to press the sheets against the spacer frame to flow the adhesive to form a moisture impervious seal having a predetermined thickness between the outer surfaces of the spacer frame and the adjacent inner marginal edge portions of the sheets. Although this procedure is acceptable for making insulating units having two glass sheets and a single spacer frame, there are limitations when the process and equipment is used to make insulating units having three or more glass sheets and two or more spacer frames.
More particularly, in the process of making a triple glazed insulating unit, a first spacer frame having a layer of a moisture impervious adhesive or sealant on opposed outer surfaces of the spacer frame is positioned between a first sheet and a first surface of a second sheet, and a second spacer frame having a layer of moisture impervious adhesive or sealant on opposed outer surfaces is positioned between a second surface of the second sheet (the second surface opposite to the first surface of the second sheet) and a third sheet to provide a subassembly. The subassembly of the triple glazed unit is conveyed though a heated oven between upper and lower heating elements to heat the adhesive to make it malleable after which the triple glazed subassembly passes between pressing rolls to bias the sheets toward one another against the spacer frames to form a moisture impervious seal having a desired thickness between the spacer frames and the inner marginal edge portions of the adjacent sheets.
The drawback with this process is that the adhesive or sealant layer between the first surface of the second sheet and the outer surface of the first spacer frame (hereinafter also referred to as the “first inner adhesive layer”) and the adhesive or sealant layer between the outer surface of the second spacer frame and second surface of the second sheet (hereinafter also referred to as the “second inner adhesive layer”) are at a lower temperature than the adhesive or sealant layer between the outer surface of the first spacer frame and the first sheet (hereinafter also referred to as the “first outer adhesive layer”) and the adhesive or sealant layer between the outer surface of the second spacer frame and the third sheet (hereinafter also referred to as the “second outer adhesive layer”). A reason for the first and second inner adhesive layers being at a lower temperature than the first and the second outer adhesive layers is that the heat has to pass through the first and the second spacer frames before the first and the second inner adhesive layers are heated.
Based on the above discussion, it can be appreciated that maintaining the temperature of the heating oven and other process parameters to maintain the temperature of the first and the second inner adhesive layers in an acceptable temperature range might over heat the first and the second outer adhesive layers. When the subassembly passes through the pressing rolls, the first and the second inner adhesive layers are pressed to the desired thickness range; however, the first and the second outer adhesive layers are more malleable due to higher temperature and one or both of the outer adhesive layers are pressed to a thickness outside of the lower limit of the desired thickness range or otherwise have a thickness outside of the lower limit of the desired thickness range due to the weight of the subassembly. Further, maintaining the temperature of the heating oven and other process parameters to maintain the temperature of the first and the second outer adhesive layers in an acceptable temperature range might under heat the first and the second inner adhesive layers. When the subassembly passes through the pressing rolls, the first and the second outer adhesive layers are pressed to the desired thickness range; however, the first and the second inner adhesive layers are less malleable due to lower temperature and are pressed to a thickness outside of the desired thickness range or might not develop the desired level of adhesion.
As can be appreciated by those skilled in the art, it would be desirable to provide an insulating unit, and method of making an insulating unit, having two or more spacer frames and three or more glass sheets that does not have the drawbacks of the presently available insulating units, and method of making insulating units, having two or more spacer frames and three or more glass sheets.